Restore from backup prompts for security key twice

[germain-gg]

Steps to reproduce

1. Go to settings, click restore from backup
2. Enter your security key
3. Wait for all the keys to be fetched
4. See you're prompted to enter your security key again
5. Enter the same one as in step 2

Outcome

What did you expect?

To not even be asked to enter my security key, as I already did it in step 2

What happened instead?

It asked me to enter my security key, and on top of that told me there was a mismatch...
But all the messages now seem to decrypt in the background, so i don't even know what this step is doing

Operating system

No response

Application version

No response

How did you install the app?

No response

Homeserver

No response

Will you send logs?

No

[turt2live]

I suspect this is related to #23931

[richvdh]

I wasn't able to reproduce this exactly as phrased: whenever I click on "Restore from backup", the key is already cached and it just tells me that it successfully restored the keys.

However I was able to reproduce something very similar as follows:

1. Start a new session
2. Do not verify the new device or enter the security key/phrase. Ignore the dire warnings and click "I'll verify later".
3. On the settings panel, click "Connect this session to Key Backup"
4. Enter your security key
5. Wait for all the keys to be fetched
6. See you're prompted to enter your security key again [Note: in this case it prompts for your key, implying the security phrase is insufficient

It turns out that if you skip over the prompt at step 6 then everything works fine.

I'll investigate this as part of my work in wiring up Key Backup in element R (#24828)

[richvdh]

Closing this in favour of #26247